01 Trans am ls1. MAC scanner shows fualt on all 8 coils ??
12-09-2018, 09:06 PM
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01 Trans am ls1. MAC scanner shows fualt on all 8 coils ?? Ok this was a 3.8 auto 2001 firebird. Bought a 2000 model ls1 and t56 complete with harness and everything to do the swap that has 50,000 miles on it. It came from a 2000 model camaro ss. That wasn't as hard as I've read about. Anyways, all installed, fired up and runs with the exception of at idle it is missing on all 8 cylinders. Above idle it sometimes runs fine, sometimes it's like it's still the 3.8. No codes other than what components I've removed such as egr air pump cats . On my scanner with live data it shows all 8 cylinders misfiring, under current misfire counters all cylinders will constantly increment. All grounds are good , battery, plugs and wires, pushrods ok, good compression check, injectors are fine. I've turned wrenches for about 20 yrs and have never come across this before. Only odd thing I can point out is after watching the live data on the misfire section is for about 20 seconds the 02s live data will freeze at zero and do nothing when i rev the engine. Everything else does as it should. One other thing is when watching live data if i unplug a single coil or the connector for all 4 coils on one side the scanner will change from fault to OK. This stumps me to no end . I cant imagine all coils being bad at once so I'm thinking it's a bad computer or there's a short somewhere. If anyone has run into this problem or something similar please chime in.
12-09-2018, 09:57 PM
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Plugs and wires are new, gapped at .050, plug wires ohm at 51 . I swapped all sensors that are compatible from my silverado with no luck or any changes. Maybe someone that does tunes will see this and point me in the right direction . I don't understand why that when I unplug a single coil or the main coil harness at the top , the scanner will show the ignition coil circuit OK. ???????? WTF?
12-10-2018, 09:31 AM
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I think you may have two problems. First is the misfire and second may be the scanner has a software glitch, my collection of Snap-on scanners will sometimes do things like this. Focus on the misfire, vacuum leaks etc.
12-10-2018, 01:35 PM
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My scanner is ok tried it on another fbody problem goes away. It's not the intake or gaskets or any kind of vacuum leak. I've done the carb spray, torch gas, and smoke machine. No leaks. Power and ground are great at the coil harness and each individual coil. I still dont understand why with the coils hooked up the scanner shows Fault on all coils but soon as u unplug one side it shows ok. If u unp6them individually wich ever coil will then say Ok.
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12-10-2018, 01:48 PM
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There is no tune, pcm is stock. U can feel it miss at idle. U can open the doors and watch them shake. If I put it in 1st and let the clutch out and let it pull itself with no throttle it goes away. Sometimes it will pin u to the seat and other times it runs like a v6
12-10-2018, 02:32 PM
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I guess that could be a possibility but I would think it would trip a code. I know moving the coils around doesn't change anything. I'm going to try one side of oils off my truck and see what happens.
12-10-2018, 02:38 PM
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So you're saying your detecting a misfire in the scanner but its not throwing a misfire code? That's just wierd....really sounds like you're missing a ground or something goofy. What do the plugs look like? Have you pulled the valve covers to look for anything loose?
12-10-2018, 02:45 PM
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No codes other than what I removed, egr air pump rear 02s. Plugs look normal, brand new . Also wires. I've bought 4 sets of plugs and wires no change, I've checked all grounds . I've even hooked them up directly to the battery no change. Pushrods and rockers are all ok. Rockers have trunion kit installed. Lifters are new all gaskets , oil pump timing chain, cam are new. Stock cam replacement. It will sit at idle and shake like the plug wires are loose. It's the weirdest misfire I've ever encountered in all my years doing this.
12-10-2018, 03:05 PM
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Might want to back probe the power and ground circuits for the pcm while it's running. See if you find anything there. Just to confirm, the pcm is the one that ran this engine in the original car it came out of?
12-10-2018, 03:26 PM
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Already checked for continuity for all the coils and the the icm circuits all checked ok by the service manual . Yea it's the same pcm that was in the car, I had the people I bought it from show me video if it running and lot drove b4 I bought the set up.
12-10-2018, 03:28 PM
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Power to all the coils hot wire are 14.5 running and 12.7 off. Grounds on all coils check the same. I think its gotta be a bad computer, I think it's not sending a good signal to fire the coils properly.